1. Field of the Invention
This invention relates to a hollow-cathode type metal ion laser for producing white light output.
2. Prior Art
Blue, green and red laser lines, which correspond to three optical primary colors, are observed under simultaneous oscillation in hollow-cathode discharge.
Appropriate control of the relative intensities of the blue, green an red laser lines can produce `white` light.
In this regard, for example, an article by Wong Kin-Hung and C Grey Morgan in Appl. Phys., entitled "`White` Light Laser", 16 (1983) L1-L4. printed in Great Britain, discloses a He-Cd.sup.+ laser system which provides simultaneous laser oscillations in the three primary colors, blue, green and red.
However, such prior white light lasers cannot produce continuous wave white light for very long, in practice. This is due to the fact that sputtered material, sputtered in hollow-cathode discharge, quickly covers the inner surface of the hollow-cathode and the insulators.
Therefore, the above-mentioned prior white light lasers are not suitable for use as a white light source in, e.g. a color display, in color photography or the like.